The present invention relates in general to a method and a system for traffic monitoring and in particular to measuring traffic intensity and congestion on roads.
During the latter part of the twentieth century with the expansion of metropolitan areas and the development of new suburban housing, society has experienced longer commuting times to work and higher vehicular congestion on the major metropolitan thoroughfares. National highway systems developed in the early part of the century have not fared any better. The unprecedented growth in vehicle ownership, coupled with public transportation and the high rate of commerce using trucking services has caused substantial congestion as well in almost all major arteries of communication. Traffic and congestion are undesirable, as they are the cause of increased pollution, additional costs to society and in many instances they contribute to accidents.
Various approaches to traffic monitoring and control are being implemented on a world-wide basis. Most of these systems employ sensors that are inherently limited in the coverage area and therefore such systems in most instances are deployed in limited critical areas and depend heavily on cameras and basic weather sensors. Vehicles are then alerted or redirected as needed via large luminous signs posted on such roadways. While these methods are improving the overall safety of some areas they do not provide a comprehensive solution to the problem of traffic and vehicular congestion monitoring. Systems that depend electronic monitoring embedded in the roadway, require a large number of sensors with the associated large investment required and in addition such solutions require constant and costly maintenance.
Radar technology is often used as means of monitoring traffic, notably air traffic. Several methods use microwave raster beams generated by a roadside sensor as disclosed in U.S. Pat. No. 3,582,620 to Noetinger; U.S. Pat. No. 3,626,413 to Zachmann; U.S. Pat. No. 4,866,438 to Knish; U.S. Pat. No. 4,985,705 to Stammler; U.S. Pat. No. 5,337,082 to Fredericks and U.S. Pat. No. 5,663,720 to Weissman. These solutions make use of radar signals. Such approaches provide more or less weather interference-free monitoring, but are mainly local solutions, which result in large investments and high maintenance costs and limit them to monitor specific areas.
Optimal routing and automated traffic mapping using a wireless network has also been used as means of gathering and interpreting information aimed at mapping traffic conditions, and is disclosed in for example U.S. Pat. No. 6,150,961 to Alewine et al; U.S. Pat. No. 5,610,821 to Gazis et al; U.S. Pat. No. 5,745,865 to Rostoker et al; JP 8221697 to Takeda Mutsuya; and JP 10307993A to Maru Shinichi. These approaches are focused on controlling traffic and routing and require dedicated communication between the mobile units and the system aimed at the acquisition of information necessary to operate such systems. The solution in U.S. Pat. No. 6,150,961 to Alewine at al requires in addition that vehicles must be equipped with a GPS unit. While such systems may provide solutions for specific applications such as providing optimal routing for an ambulance, the nature of the information acquisition is such that a generalized mapping system would require agreement by a large number of vehicles equipped with wireless units to regularly provide such information. Such agreements are likely to be expensive to implement and more likely not possible to implement in a homogeneous manner over different areas, which negate the ability to generate large area mapping information. In U.S. Pat. No. 6,150,961, the use of wireless infrastructure to provide feedback from GPS units is specifically considered, which could generate location and therefore velocity data from moving vehicles, again communication between the vehicles and the data acquisition system is obtained to communication dedicated to this specific end. Such approach would prove often impractical to implement. In addition, it would be necessary to have installation of such units in a sufficiently large number of vehicles to generate meaningful data, which would, in any case, limit the acquisition of data to areas where the units are outfitted and circulate at any point in time.
It is therefore an object of the present invention to provide a method and system for traffic monitoring which is not limited to usage of dedicated devices located in a selection of vehicles, overcoming the above-mentioned problems.
The objects are achieved by the methods and systems according to the appended claims.
According to the invention, a method for traffic monitoring comprises the steps of: determining at least twice, within a specified time interval, geographical positions of a plurality of mobile devices in a mobile telecommunications network by means of measuring at least one property of signals transmitted between said mobile devices and base stations in said mobile telecommunications network; comparing at least a subset of said geographical positions with a route of a road provided in a route database in order to identify mobile devices having routes corresponding to at least a part of said road route; calculating a velocity for said identified mobile devices based on said at least two positions; and comparing said calculated velocity of at least one identified mobile device with a reference velocity of said road in order to monitor and predict traffic intensity on said road.
Hereby a method is provided which makes traffic monitoring of almost any road having coverage of a mobile telecommunications network feasible. The inventive method takes advantage of the large amount of users of mobile devices, such as mobile phones or other wireless devices in a telecommunications network, and the signals that are transmitted between these devices and a plurality of base stations with known locations. The locations of the base stations tend to follow transit arteries, such as highways, where conversations and usage of wireless services is likely to take place. Further, many mobile devices are located in vehicles, such as cars, trucks, buses, etc, or carried by persons located in such vehicles. Analyzing these signals in conjunction with the information where base stations are located in relation to roads and highways, it becomes possible to monitor the traffic on virtually any road covered by a mobile telecommunications network. The invention will benefit from the higher potential frequency reuse in third generation mobile telecommunication systems coupled with capacity requirements for new wireless applications, which will result in further increase in the density of base stations in urban areas and highly trafficked thoroughfares further enhancing the data-gathering ability of the proposed method.
Basically, there are two techniques for positioning a mobile device using a mobile telecommunications network, terminal based or network based. Network based solutions do not require a special kind of handset which would imply that all radio signals to and the wireless network could be used to compute traffic patterns. The present invention particularly benefits from the network based positioning, which eliminates specialized software in the mobile devices. Examples of network based solutions include the Cell Global Identity and Timing Advance (CGI+TA) and the Uplink Time of Arrival (ULxe2x88x92TOA) methods. Furthermore, Doppler Shift from the radio signal of a mobile device can be used to estimate location and speed of vehicles. With the advent of GPRS technology in second generation wireless networks and the resulting xe2x80x9calways onxe2x80x9d conditions for the wireless users, the data flow to the network will be substantially increased. Third generation (3G) systems will further enhance these characteristics.
Then, the positions of a mobile device is compared with information about road routes and their geographical relationship with the base stations. The positions of base stations are in general known, and these positions could either be stored in the road route database or provided with the information about the position of a specific mobile device. Given at least two, and preferably more, locations of a mobile device, it becomes possible to compare these with the route of a road. If they all fit along the route, or at least a part of a route, and it is possible to determine whether the mobile device possibly could be travelling along the road based on this information, the data about the mobile phone and its movements could be further analyzed.
In order to predict the traffic intensity on a road, information about the velocities of the mobile devices that are travelling along the route of the road is used. For example, the highest measured velocity could be compared with a reference velocity. Instead of using the highest obtained velocity, an average of a group of high velocities can be used for comparing with a reference velocity for a road. The reference velocity could be the maximum allowed speed, the highest historical measured speed, a speed which is typical for that time of the day, etc. Then, if the traffic travels at for instance 30% of the reference speed, the road is probably congested and the traffic is intense. Thus, the invention uses the vehicles"" speeds in relation to a reference speed as a measure of how intense the traffic is. In another embodiment, the number of vehicles passing a section of a road per time unit could be a measurement of how intense the traffic is.
Preferably, some sort of filtering is performed to remove those mobile devices, which move along the route of a road, but cannot be assumed to be located in a vehicle, for example carried by a pedestrian or a cyclist. This could be-done by excluding those measurements which relate to mobile devices having a velocity below a certain limit, for example 20 km/h.
To enhance measurement accuracy, prior measurement readings could be used in the specific areas of interest to filter relevant data and further enhance the accuracy of location-specific readings.
With the invention it becomes possible to provide a graphical map of both current and historical traffic conditions, which could be used by individuals, companies or institutions, to determine optimal vehicular routing. The traffic intensity could then be represented by colors describing the level of intensity.
According to the invention a system for traffic monitoring, comprises: positioning means for determining at least twice, within a specified time interval, geographical positions of a plurality of mobile devices in a mobile telecommunications network by means of measuring at least one property of signals transmitted between said mobile devices and base stations in said mobile telecommunications network; means for comparing at least a subset of said geographical positions with a route of a road provided in a route database in order to identify mobile devices having routes corresponding to at least a part of said road route; means for calculating a velocity for said identified mobile devices based on said at least two positions; and means for comparing said calculated velocity of at least one identified mobile device with a reference velocity of said road in order to predict traffic intensity on said road.
Hereby a system is provided overcoming the above-mentioned problems. The system has essentially the same advantages as the inventive method described above.
Also according to the invention, a solution is provided for traffic monitoring where the above-mentioned method and/or system is not feasible, which also takes advantage of existing infrastructure. This is accomplished by a system for traffic monitoring of a road comprising: at least one fixed transceiver located near said road having a coverage area covering essentially the full width of said road, being adapted to communicate with a transceiver located in a vehicle moving on said road; means for measuring the time difference between establishing of contact and loss of contact with a transceiver moving through said coverage area; means for calculating a velocity of said moving transceiver based on said time difference and information about said coverage area; and means for comparing a calculated velocity of at least one moving transceiver with a reference velocity of said road in order to predict traffic intensity on said road.
Such a system makes it possible like the above-mentioned method and system to utilize existing infrastructure in society. Preferably, the fixed transceiver and the moving transceiver are units using BLUETOOTH(trademark) wireless technology, or at least working according to the same principles as defined by the BLUETOOTH(trademark) standard.
The automotive industry is in the process of incorporating BLUETOOTH(trademark) technology in nearly all vehicles. We can expect in the very near future that such modules will be placed in all produced vehicles. As a part of the general agreement for BLUETOOTH(trademark) standard, it is contemplated that each BLUETOOTH(trademark) unit has a unique identity. Equipment enabled with BLUETOOTH(trademark) technology will automatically search the vicinity for other BLUETOOTH(trademark) compliant equipment. On contact, information is exchanged allowing the system to determine weather or not to establish a more specific connection. At this first encounter the BLUETOOTH(trademark) devices transmit a personal identification number. Up to eight devices can operate simultaneously within a BLUETOOTH(trademark) cell. Hence in areas where the wireless network cannot provide proper data flow, BLUETOOTH(trademark) modules are installed in the vicinity of the monitoring areas and these units monitor vehicles equipped with BLUETOOTH(trademark) modules and provide the required data to the system.
Then, the system uses a trimmed signal amplifier and/or directed antenna to only cover a specific part of a road. When a BLUETOOTH(trademark) equipped vehicle then passes along the road which is covered by the range of this antenna, the time difference between making and loosing contact with the fixed BLUETOOTH(trademark) module is measured. In advance, the distance between those positions along the road where the threshold is sufficiently high to obtain contact between a moving BLUETOOTH(trademark) module is measured. This information now serves as a base for calculating the velocity of vehicles passing by. Then, intensity and congestion is determined by comparing the velocity of passing vehicles with a reference velocity. The analysis, filtering, etc of mobile device velocity is similar to the above-mentioned method.
Preferably, the coverage area of the fixed BLUETOOTH(trademark) unit is a substantially rectangular shaped band substantially perpendicular to the direction of said road provided by an directed antenna.
Preferably, the system comprises two fixed BLUETOOTH(trademark) units located between the lanes of opposite directions having their antennas directed towards respective roadside.